Stone preservation with illustrative examples from the United Kingdom

Interest in the preservation of rapidly decaying monuments, especially in urban areas, has increased appreciably over the last three decades. A stone preservative can be defined as a chemical treatment, which, when applied to stone, combats the harmful effects of time and environment, thereby prolonging the life of a stone by either restoring its physical integrity or by inhibiting its decay. Any preservative applied to stone must not change the natural appearance or architectural value of the stone to any appreciable extent. There are two principal means by which stone can be preserved. One involves the formation of an outer stabilized zone around the stone; the other alters the chemical composition of the stone.A number of examples of stone preservation carried out on ancient monuments in the United Kingdom are taken to illustrate stone preservation methods. Their relative success is evaluated, and some more recent developments in stone preservation referred to.